Destruction of crab grass



Patented Aug. 26, 1952 DESTRUCTION F CRAB GRASS Loyd Q. Boyd, Hammond, Ind., and Albert A. Endres, Homewood, 111., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application October Serial N0. 192,620

8 Claims. 1

I'hisinvention relates to an improved method and means for destroying crab grass and it permore particularly to compositions and their method of application to lawn turf for destroying crab grass without destroying blue grass or other desired grasses.

Crab grasses (Digitdrz'a sanguinalis and digita'rta tsc'haemum) are major weed pests of lawn turf: throughout most of the United States. They have presented home owners and others concerned with the growing of grassed areas with one of their most difl'icult and persistent problems, Many weed killers are effective against all vegetation and certain weed killers (such as 2,4-Dl are effective against broad leafed weed pests but not against narrow leafed grasses; such prior herbicides or weed killers have not been effective for destroying crab grass without unduly injuring blue grass, bent grasses or other grasses which are desirable in lawn turf. The object of our invention is to solve the problem of destroying crab grass in lawn turf Without undue harm to blue grass or other desirable grasses.

We have discovered that thiocyano ethers and esters of types previously known to the art as insecticides have the remarkable and surprising.

property of selectively destroying crab grass when applied to a lawn turf in proper concentration. These thiocyano ethers and esters may be applied either in an aqueous medium or a hydrocarbon medium such as a saturated hydrocarbon fraction boiling in the range of about 250 to 500 F. When employed in an aqueous medium they are preferably emulsified in water and applied in concentrations of about 1 to 4 volumes oi' the thiocyano ester or ether per 100 volumes or water. When employed in a hydrocarbon oil, the amount of thiocyano ester or ether should be in the range of about .2 to 2% by volume. Best results are obtained by applying the aqueous emulsion or hydrocarbon solution in an amount suillcient to apply about 1 to 2 gallons of dithio'cyano esters or ethers per acre, this amount being in the range of about i to 4 gallons per acre when applied in an aqueous medium and in amounts of about .1 to 2 gallons per acre when applied in the saturated narrow boiling hydrocarbon distillate.

The thlocyano ethers which we have found to be most efl'ective are such compounds as betabutoxy-beta-thiocyanodiethyl ether (C4HcOCH2CHzOCHzCH2SCN) beta-beta-dithiocyanodiethyl ether (NCSCH2CH2OCH2CH2SCN) and the like, which are well-known insecticides. Examples of thiocyano esters are isobornyl thiocyano acetate, fenchyI-thiocyano acetateand beta-thiocyano ethyl esters of aliphatic acids, preferably containing 10 to 18 carbon atoms per molecule. Other organic and particularly aliphatic thio'cyanates having the equivalent toxic properties may be employed, but we have found that inorganic thiocyanates, such as potassium thiocyanates and ammonium thiocyanates are unsuitable since they destroy unduly large amounts of blue grass and other desirable grasses in the turf. Organic thiocyanates employed for insecticidal purposes are limited in number because many members of the class are skin irritants so that they cannot be applied to animals; since our composition is not intended for use as an insecticide and is not to be applied to animals, any skin irritating tendencies are of no consequence. Our invention, however, is particularly applicable to the thiocyano ethers and esters of the type hereinabove set forth.

It has recently been discovered that refined saturated hydrocarbon dlstillates boiling; entirely within the range of 350 to 500 F. are per se quite effective for crab grass control. Such an oil has been applied to the turfat about mid summer when the crab grass plants first became noticeable or were about 1 to 2 inches in length. In this case the oil was applied three times at 10 day intervals using a total of 240 gallons per acre. The spraylng with such oil has also been effected when the crab grass was nearly ready to form seed heads and in this case only two sprays were used, the total again being 240 gallons per acre. We have tound that our improved sprays are effective in a single application and that they give results which are even better than the multiple spray procedure heretofore practiced.

Our aqueous emulsion or hydrocarbon. solution should be applied in such a way as to insure the wetting of the crab grass. Generally, the spray o1 course, be so proportioned so as to provide uniform coverage at the rates hereinabove defined, i. e. about 80 gallons per acre or sufiicient to distribute about 1 to 2 gallons of the dithiocyano others or esters per acre.

Under conditions where grass is so tall that it is difficult to restrict the gallonage applied to as little as 80 gallons per acre, more water may be added to the aqueous emulsion or the hydrocarbon oil solution may be emulsified in water to secure the larger liquid gallonage needed. For example, 80 gallons of the oil solution may be emulsified in 69 gallons of water by means of 1 gallon of sulionated castor oil or other suit- ,able emulsifying agent.

As a specific example 'ofour invention; tests were made on a plot containing a number of crab grass plantsin a turf-also containing blue grass, bent grass, etc; -The base oil-employed in these tests was a hydrocarbon distillate having 0% unsaturation, an initial boiling point of 352 F,, a 10% point of 380 R, a 50% point of 4'10 F.', a 90% point of 440 and an end point of 480 F. -The sprays in all cases were applied at the rate of 2 quarts per square rod and where two applications were applied, the second application was after a 14 day interval. A careful check was made of the condition of the various grasses at variousintervals of time and the data obtained in these tests is set forth in the following 40 4 days had elapsed and the kill increasing to after 42 days but that there was no apparent eiiect for the first Week or two. When the base oil was applied twice with a 14 day interval, the ultimate kill was 78.5% and the per cent regrowth, which amounted to 21.5%, was smaller than in the case of a single application. The base oil containing 1% of beta butoxy-beta-thiocyano diethyl ether applied in only a single application effected a crab grass kill of 65% after 10 days, the kill being up to 91% after 14 days, 95% after 21 days and 99.5% after 42 days. The'regrowth was practically nil when 1% of the thiocyano ether was added to the base oil. Thi remarkl5 able increase in crab grass kill and prevention of crab grass regrowth with only a single application of the spray oil was accompanied by a somewhat increased retarding of the other grasses. The thiocyano ether composition caused somewhat greater retarding of blue grass or bent grass for the first 21 days but at 28 days 90% of the blue grass and 60% of the bent grass was recovered from single application treatments. By 42 days, the blue grass and bent grass were about 90% recovered in the test employing thiocyano ether. While the blue grass recovery was somewhat better with the single. applicationof'base oil, test 1 was'rnarkedly superior to theiapplica- .tion of 2 base oil sprays in other words a single application of the base oil itself didnot produce the desired crabgrass killand 2 applications of the base oil were more detrimental to blue grass and bent grass while still failing to accomplish the crab grass kill attained with only 1 application of base oil containing thiocyano ether.

Another series of test data is reported in the following Table II wherein spays were likewise applied at the rate of 2 quarts per square rod (about gallons per acre), wherein the base oil table. Was the same as that employed in the first series TABLE I Selective control of crab grassG1-eenhouse tests [Grass clipped twice to 2 inches before treatments] Days after Initial Treatments N0. 10 14 21 28 42 Test Material Applications Plants I Percent Percent Percent Percent Percent 7 Percent Percent Percent Dead Dead Dead Regrowth Dead Regrowth Dead Regrowth 1. a Base OiH- 1 163 65.1 91. 0 95. 5 0.0 95. 5 O. 5 99. 5 0. 5

, 1% b buto xy -b thiocyanodiethyi ether. 2 Base Oi1 1 00 0.0 11.7 58.4 35. 0 60. 0 38. 3 70. 0 30.0 3 Base Oil. 2 172 0.0 i 5.8 54.0 25.6 67.0 29.6 78.5 21.5 4"... Untreated" None 100 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

First application was made when approximately 95% of the crab grass plants were flowering Condition of Blue Grass Sevgrcly retard- No change from 10 days e S o m e what more retarded in test :13 than in 2 and Condition of Bent Grass Approximately 15% necrosis and 15% chlorosis.

' From results set forth in'the above table, it will be noted that the single application of the base oil per se (test 2) was effective in killing No change from 10 days 60% recovered'irorn 1 application treatments but severely retarded from 2 applications and showing 25% necrosis.

% recovered from 1 application and 83% recovered from two applications of Base 011; 93% recovered from test 1.

of tets and wherein the kerosene was one having substantially the same boiling range as the base. oil. The results of this second series of tests about 60% of the crab grass after a period of 28 7 5 Were as follows:

serum v crab gran -Greenhouse [Grass clipped toainches before treatments.) I

Days After Initial Treatment 14 1 I.) a, A.

l i Percent If rcent li er-cent Percent A hercent Pei-q t. Percent f Dead Regrowth Dead Regrowth Dead -3 A 90% b-butoxyb-thio- 1-5o 102 55.1 77. a 17.6 74. 5 2s. a 75. 5 2'4. 5

cyano diethyl ether+ B 1% gb;butoxy-b'-thio- 13 147 -:0. 35. 4 55. 6 28. 71. 5 42. 3 57. 8

cyano diethyl ether+ Kerosene. O- 91% b-butoxy-b'-thio- None 116 -6. 9 60. 9 19. 8 60. 8 89. 7 71. 6 28. 4

cyano diethyl ether f in 13356 Oil. f D- 54% isobomyl thio None 118 312.7 72.0 6.8 90.0 I 10.0 9142 8.8

rgxlmo acetate in Base 1 l E Untreated 125 0.0 0.0 0.8 0.8

Condition oi Blue Grass PllogtsnfB, and Plots A, B, and E Plots A, B, and E nor- Plots A and B 100% n o r m a Plots 0 and D retarded. t

Condition of Bent Grass All 1' mal.

In this series of tests the crab grass kill was somewhat less than in the first series of tests :but nevertheless it was remarkably high. The isothiocyano ester employed in plot D is shown in thesetests to be even more effective than the thiocyano ether of plot C. The emulsifleremployed in the compositions used on plots A and B was a mixture of poly-oxyethylene sorbitol oleate and laurate, but it should be understood that sulfonated castor oil or any other suitable emulsifier may be employed.

Where the base oil contains 1% of the thio cyano ether or ester and is applied at the rate of about 80 gallons per acre, it will be apparent that the thiocyano ether or ester itself is used in an amount of about .8 gallon per acre. When such base oil is employed as the carrying medium for the thiocyano esters or ethers, the amount of said thiocyano esters or ethers per acre should be at least about .1 gal. for substantial eifectiveness, but it should not exceed about 1 or 2 gallons per acre. When applied as an aqueous emulsion in the absence of oil, we have found that best results are attainable when about 1 to 4 volumes or thiocyano esters or ethers are emulsified in 100 volumes of water and the emulsion is applied-in quantities suiiicient to app y. about 1 to 4 gallons of the thiocyano ester or ether itself per acre of grass turf. In other words, the base oil itself has a substantial killing power for crab grass and it also apparently enhances the effectiveness of the thiocyano esters and ethers when the latter are employed in base oil solution. The nature of the base oil solution is, of course, very important because lighter oils volatilize too rapidly'and heavier oils tend to cause injury of desirable grasses. The absence of any appreciable amount of sulfonatable components is also essential in the base oil since sulfonatable components cause injury of desirable grasses. The base oil solutions should in no case be applied to turf at a rate substantially exceeding 150 gallons per acre and advantageous results are obtainable with a gallonage as low as 50 gallons per acre, a preferred dosage being in the range of about 80 to 100 gallons per acre with normal. PlotsC and D severely retarded.

mal. Plots 0 and D severely. retarded. Plot C-3% necrosis.

plots n'or- Plots A and E nor- Plots A, B, and E nor- Plots A and B remal Plot )3 mal. Plot 0 severely covered. Plot 0 97% slight chlorosis. retarded 3% Nee. recovered. Plot D Plots 0 and D Plot D severely re- 95% recovered. Plot severely retarded. tarded'8% Nee. E Normal.

a base oil containing 1% to 2% of the organic thiocyanate dissolved therein.

We claim:

1. The method of selectively destroying crab grass in a grass turf containing crab grass and other grasses, which method comprises applying to said turf in a carrier liquid about .1 to 4 gallons per acre of a' compound selected from the class consisting of thiocyano esters and ethers.

2. The method of claim 1 wherein the carrier liquid is water and the compound is applied in amounts of about 1 to 4 gallons per acre.

3. The method of claim 1 wherein the carrier liquid is a refined base oil boiling substantially entirely in the range of 350 F. to 500 F. and substantially free from sulfonatable components and wherein said compound is applied in amounts of .1 to 2 gallons per acre.

4. The method of selectively destroying crab grass from a turf containing crab grass and desirable grasses, which method comprises applying to said turf in a carrier liquid an amount in the range .1 to 4 gallons per acre of a compound selected from the class consisting of thiocyano esters and ethers which amount is sufficient to kill most of the crab grass without killing as much as 25% of the other grasses.

5. The method of selectively destroying crab grass from a turf containing crab grass and desirable grasses, which method comprises applying tosaid turf at least 50 but not more than gallons per acre of a .1 to 2% solution or an organic thiocyanate in a refined hydrocarbon oil, said organic thiocyanate being selected from the class consisting of thiocyano ethers and esters and said oil boiling within the range of 350 to 500 F. and containing substantially no suli'onatable components.

6. The method of claim 5 wherein the organic thiocyanate is beta-butoxy-beta'-thiocyano diethyl ether.

'7. The method of claim 5 wherein the organic thiocyanate is beta-beta'-dithiocyano diethyl ether.

8. The method of claim 5' wherein the organic 7 s thiocyanate consists essentially of isobornyl thio .7 Number Name Date cyano acetate. 2,111,581 Bray Mar. 22. 1938 LOYD- Q. BOYD. 2,405,775 1 vBradley Aug. 13, 1946 ALBERT A. ENDRES. I 2,467,235 Searle Apr. 12, 1949 REFERENCES CITED OTHER REFERENCES U. S. Dept. of Agriculture, Bur. Entomology g g i fi are of record m the and Plant Quarantine, Div. of Insecticide Investigations, Bull. #E 344,:by'Roa1-ket aL, page 46, UNITED STATES PATENTS 10 May 1935 7 Number Name Date 1,808,893 Heckert June 9, 1931 

1. THE METHOD OF SELECTIVELY DESTROYING CRAB GRASS IN A GRASS TURF CONTAINING CRAB GRASS AND OTHER GRASSES, WHICH METHOD COMPRISES APPLYING TO SAID TURF IN A CARRIER LIQUID ABOUT .1 TO 4 GALLONS PER ACRE OF A COMPOUND SELECTED FROM THE CLASS CONSISTING OF THIOCYANO ESTERS AND ETHERS. 